There were reports (like this
) about how even with similar usage Androids sucked more data than the iPhone, and the thought was that some of it was inefficient handling and some was 'phantom' stuff like over-zealous polling and so on.
The WP7 concern was about how much stuff was 'cloud based' and especially all of those live tiles. But so far there is no huge outcry about it, with one blogger
showing no more use than the iPhone ... but it is hard to call that even a 'sample', let alone representative or statistical!
I couldn't find much else from after the WP7 launch, so we will have to wait a while to know for sure.